1. Field of the Invention
The invention is directed to the field of continuously variable transmissions.
2. Description of Related Art
Variable transmissions are known in the art for converting an input torque and velocity to an output torque and velocity over a wide range of input-to-output ratios. In a continuously variable transmission, there is a smooth transition from input to output over a spectrum of ratios, as opposed to discrete incremental ratios as with conventional transmissions. Examples of infinitely variable transmissions include the Letters Patent to Pires, U.S. Pat. No. 5,334,115; the Letters Patent to Mercat, U.S. Pat. No. 5,081,877; the Letters Patent to Genovese, U.S. Pat. No. 5,071,393; and the Letters Patent to Coronel, U.S. Pat. No. 5,352,162.
The Pires patent describes a variable transmission relying on an oscillating ratchet. Pires teaches a plurality of different successive intermediate rotations that vary in velocity and direction in accordance with their own respective oscillatory wave form, each waveform being out of phase with one another in a predetermined way. These intermediate rotations are used to convert the rotational input to a plurality of uni-directional output rotations, without the use of over-running clutches. The outputs vary in velocity in accordance with their own respective waveforms and are used to produce a modified rotational output.
The Genovese patent purports to show a variable ratio transmission with a stationary housing having a variable diameter internal surface and an input and output shaft journalled in the housing for rotation abut a common axis co-axial with the variable diameter internal surface of the housing. A floating eccentric mounted on the input shaft has an external cylindrical surface with the eccentricity of that cylindrical surface with respect to the input shaft being variable between approximately co-axially with the input shaft to a maximum preset eccentricity. A drive member supported co-axially on the floating eccentric has an external cylindrical surface in rolling engagement with the internal of the variable diameter internal surface and coupled to the output shaft. The rotational velocity ratio of the Genovese device between the input and output shaft is varied by varying the diameter of the internal cylindrical surface of the housing and correspondingly varying the degree of eccentricity of the floating eccentric to the input shaft.
The Mercat patent discloses a variable transmission in which a driving element and a driven element are adjustable eccentrically to one another and are coupled via pivotal levers which are journalled on one element and can be brought into force transmitting clamping engagement with the other element via coupling shoes. The two change velocity units are inversely combined with an eccentric positioning device which either jointly actuates the members with the ring tracks associated with the coupling elements or the members with the coupling elements. The force transmitting zones of engagement of the two units are angularly displaced relative to one another and the eccentricities of the two units and also the lever arms associated with the coupling elements can be so selected that transmission ratios result which are free of fluctuations.
The Coronel patent discloses a dual concentric positively infinitely variable transmission which uses a user actuated control to vary the transmission output. The input control varies the orbital relationship and effective gear ratio between a driving ring gear and a driven pinion gear causing both gears to variably orbit the mechanism central axis to produce an output receiving gear and connected output shaft torque converting velocity range, where the velocity varies between a geared neutral stopped position and its maximum output velocity.
The aforementioned devices are complicated, cumbersome transmissions which are difficult to control and were limited to low horsepower. The design of the present invention is to overcome the shortcomings of the prior art of continuously variable transmissions by teaching a simple, compact design having more versatility than previous transmissions.
The present invention can be used to increase or decrease an input rotational velocity along a continuous spectrum using an eccentric cam and a plurality of overrunning clutches. In a first embodiment, a cam plate with an annulus can be pivoted from a concentric to an eccentric position. A plurality of planet gears have crankshafts which are actuated when the cam plate is pivoted in an eccentric position, but are not actuated when the cam plate is in the concentric position. The crankshafts rotate through an angle on their own axis at different speeds, depending on the cam plate eccentricity, as the cam plate orbits eccentrically during a cycle. Each crankshaft drives a one-way overrunning clutch which rotates the planet gears, which drive a sun gear engaged with the planet gears. The sun gear is driven at a minimum by an input velocity by the carrier, and is augmented by the planet gear with the highest rotational speed. The remaining planet gears are then driven by the sun gear as the overrunning clutches relinquish control to the fastest rotating planet gear. The ratio of the output velocity to the input velocity is controlled by the amount of eccentricity of the cam plate, and the spectrum of ratios is continuous over a range.
In a second embodiment, an input velocity drives a cam bearing at input velocity, and the cam bearing can be pivoted from a concentric position to an eccentric position. In the concentric position, crankshafts actuated by an orbiting of said cam plate bearing are not actuated when said cam bearing is in a concentric position, and unlike the previous embodiment the sun gear is not driven at input velocity, resulting in a zero velocity output. However, as the cam bearing is pivoted into an eccentric position, the crankshafts are actuated serially as the cam bearing orbits, and each crankshaft imparts a rotation to its associated planet gear. Each rotation of a planet gear in turn rotates the sun gear which drives the output velocity. The ratio of the output velocity to the input velocity varies between zero and one for this latter embodiment. In a third embodiment, the transmission of the second embodiment is actuated with an actuator rod which drives the cam bearing from a concentric position to an eccentric position.